1. Field of the Invention
The present invention relates to an object, a method, or a manufacturing method. In addition, the present invention relates to a process, a machine, manufacture, or a composition of matter. One embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a memory device, or a driving method thereof. In particular, one embodiment of the present invention relates to a semiconductor device, a display device, or a light-emitting device each including an oxide semiconductor.
In this specification and the like, a semiconductor device generally refers to a device that can function by utilizing semiconductor characteristics. A display device, an electro-optical device, a semiconductor circuit, and an electronic device include a semiconductor device in some cases.
2. Description of the Related Art
Much attention has been focused on a semiconductor device that retains data by using a combination of a transistor in which silicon (Si) is used for a semiconductor layer and a transistor in which an oxide semiconductor (OS) is used for a semiconductor layer (see Patent Document 1).
In recent years, with the increase in the amount of data manipulated, a semiconductor device having a large memory capacity has been required. In this situation, Patent Document 1 discloses a semiconductor device where multilevel data is stored and read.